leaving cert physics

Leaving Cert Physics exam – final advice

Looking for a top grade?

Just one day to go.

Wondering what topics to concentrate on?

Consider the following:

Electromagnetic Induction has appeared on past exam papers on the following years:

2011 —

2010 —

2009 —

2008 no.8

2007 12 (c)

2006 no.11 {5/8 of a long question}

2005 12 (b)

2004 12 (c)

2003 12 (d)

2002 12 (c)

That’s right – it’s appeared every year from 2002 to 2008 but not for the last 3 years – don’t go into the exam without knowing it back to front and upside down. The document which contains all past questions on this topic together with the worked solutions can be found on the revision page of thephysicsteacher.ie.

How about The Electron?
Let’s take a look:

2011 —

2010 no.9

2009 no.8

2008 no.11{5/8 of a long question}

2007 —

2006 12 (d)

2005 12 (d)

2004 no.9

2003 no.9

2002 no.9

So most years it’s a full question, but hasn’t appeared last year at all. Same advice therefore – see all questions and solutions on the revision page of the website.

Particle Physics comes up every year – this year was the 75th anniversary of the Cockroft and Walton experiment – pay particular attention to past questions on this topic.

In fact for a full overview of all questions likely to appear this year (tomorrow!) you could do worse than check out the following:

If you want to download this document then the link is here

And remember – expect the unexpected. If something comes up that you haven’t seen before then just deal with it. Welcome to the real world!

And good luck with it 🙂

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The nature of matter

Few concepts in Physics generate wonder quite like Quantum Theory. You only need to look at the shelves in the Popular Science section of a bookstore for evidence. Yet (once again) in schools we play down this sense of wonder. I used to think this wasn’t done deliberately but now I’m beginning to learn that there was once a school of thought that believed in doing exactly that, particularly for Science (more on that later).

Anyways, one of the most incredible ideas in Quantum Theory concerns the nature of matter itself – is it a particle or is it a wave?
For light, we can prove that it’s both (ridiculous though that may sound) and indeed students are expected to know the demonstrations which verify both. There is however no suggestion anywhere in either the textbooks (that I have come across) or in the syllabus that there is anything slightly disturbing in this. There was a single question on the exam paper once which asked why was Quantum Theory considered revolutionary, but that was it. No other reference to what is one of the greatest mysteries of science; how can something be both a particle and a wave. Why do I seem to be the only one who feels so frustrated by this?

So in an attempt to pass on some of this sense of wonder for the microscopic world, I put together the following set of demonstrations for my sixth years on the last day of term. It’s about 22 minutes long so is in two parts. Forgive its amateur appearance.

How to get 100% in your leaving cert Physics exam. Part 3: Short Questions

Question 5 on the paper is 56 marks and counts for 14% of the overall mark. The choice is to do 8 questions out of 10. It is one of the more popular questions on the paper.

I have compiled a list of all the short questions which have been asked over the last ten years,  together with their solutions. It is a detailed document (26 pages) but is worth knowing not only because it prepares you for Question 5, but also because it provides a comprehensive overview of all the topics on the course itself.
I have included the years with the questions because it helps to identify the questions which are particularly popular with the examiners.
e.g.

State The Principle of Conservation of Momentum.
[2002][2009 OL][2008 OL][2007 OL][2005 OL][2004 OL]
In any interaction between two objects, the total momentum before the interaction is equal to the total momentum after the collision, provided no external forces act.

And to my mind the two most popular questions at higher level:

What is the Doppler effect?
[2008] [2007] [2006] [2003] [2002]
The Doppler Effect is the apparent change in frequency due to relative motion between source and observer.

Define electric field strength.
[2009][2007] [2005] [2003] [2002]
Electric field strength is defined as force per unit charge.

There are a lot there so don’t try to learn them all at once; take a couple of pages each day, but then make sure you keep going over them (from the beginning each time) and in no time you’re confidence will be sky high!

Try to print two pages onto one sheet, and also back to back if possible to save paper.

Junior Cert Science: Unusual demonstration of magnetic fields

This week we looked at a concept called ferromagnetism which allows us to demonstrate the 3-dimensional nature of magnetic fields.

Thanks to my first years for being so co-operative 🙂

Here’s another way of illustrating the idea (which we didn’t do)

How to get 100% in your Leaving Cert Physics exam. Part 2: Answering Graph Questions

The following can be downloaded as a word document here

Drawing the graph

  • You must use graph paper and fill at least THREE QUARTERS OF THE PAGE.
  • Use a scale which is easy to work with i.e. the major grid lines should correspond to natural divisions of the overall range.
  • LABEL THE AXES with the quantity being plotted, including their units.
  • Use a sharp pencil and mark each point with a dot, surrounded by a small circle (to indicate that the point is a data point as opposed to a smudge on the page.
  • Generally all the points will not be in perfect line – this is okay and does not mean that you should cheat by putting them all on the line. Examiners will be looking to see if you can draw a best-fit line – you can usually make life easier for yourself by putting one end at the origin. The idea of the best-fit line is to imagine that there is a perfect relationship between the variables which should theoretically give a perfect straight line. Your job is to guess where this line would be based on the available points you have plotted.
  • Buy a TRANSPARENT RULER to enable you to see the points underneath the ruler when drawing the best-fit line.
  • DO NOT JOIN THE DOTS if a straight line graph is what is expected. Make sure that you know in advance which graphs will be curves.
  • BE VERY CAREFUL drawing a line if your ruler is too short to allow it all to be drawn at once. Nothing shouts INCOMPETENCE more than two lines which don’t quite match.
  • Note that examiners are obliged to check that each pint is correctly plotted, and you will lose marks if more than or two points are even slightly off.
  • When calculating the slope choose two points that are far apart; usually the origin is a handy point to pick (but only if the line goes through it).
  • When calculating the slope DO NOT TAKE DATA POINTS FROM THE TABLE of data supplied (no matter how tempting!) UNLESS the point also happens to be on the line. If you do this you will lose beaucoup de marks and can kiss goodbye any chance of an A grade.

 

 

What goes on what axis?

Option one

To show one variable is proportional to another, the convention is to put the independent variable on the x–axis, and the dependant variable on the y-axis, (from y = fn (x), meaning y is a function of x). The independent variable is the one which you control.

 

Option two

If the slope of the graph needs to be calculated then we use a difference approach, one which often contradicts option one, but which nevertheless must take precedence. In this case we compare a formula (the one which connects the two variables in question) to the basic equation for a line: y = mx.

See if you can work out what goes on what axis for each of the following examples (they get progressively trickier):

  1. To Show Force is proportional to Acceleration
  2. Ohm’s Law
  3. Snell’s Law
  4. Acceleration due to gravity by the method of free-fall
  5. Acceleration due to gravity using a Pendulum

 

There is usually a follow-up question like the following;

“Draw a suitable graph on graph paper and explain how this verifies Snell’s Law”.

There is a standard response to this;

“The graph of Sin i against Sin r resulted in a straight line through the origin (allowing for experimental error), showing Sin i is directly proportional to Sin r, and therefore verifying Snell’s Law”.

 

If you are asked any questions to do with the information in the table, you are probably being asked to first find the slope of the graph, and use this to find the relevant information.

 

 

How to get 100% in your Leaving Cert Physics exam. Part 1: Section A

Section A counts for 30% of your overall mark and is the easiest section to pick up full marks. There are about 24 experiments but many of them are minor variations on each other. Stop wasting time trying to predict which ones will come up and just learn them all. Take one or two per night and make sure you can answer every question on each experiment from past papers. In particular you need to use the following as a checklist for each experiment.

(i)     Draw a fully labelled diagram which includes all essential apparatus (have you included the apparatus necessary to obtain values for both variables?).

(ii)   Be able to state how the two sets of values were obtained (this is a very common question).

(iii) Describe what needs to be adjusted to give a new set of data

(iv) Write down the relevant equation if there is one associated with the experiment.

(v)   Be able to state how the data in the table will need to be adjusted.

(vi) Know what goes on each axis.

(vii)           Know how to use the slope of the graph to obtain the desired answer.

(viii)         Be able to list three sources of error/precautions.

Misc Points

  • The graph question is usually well worth doing.
  • Learn the following line off by heart as the most common source of error: “parallax error associated with using a metre stick to measure length / using a voltmeter to measure volts etc”.
  • Make sure you understand the concept of percentage error; it’s the reason we try to ensure that what we’re measuring is as large as possible.
  • There is a subtle difference between a precaution and a source of error – know the distinction.
  • When asked for a precaution do not suggest something which would result in giving no result, e.g. “Make sure the power-supply is turned on” (a precaution is something which could throw out the results rather than something which negates the whole experiment).
  • To verify Joule’s Law does not involve a Joulemeter
  • To verify the Conservation of Momentum – the second trolley must be at rest.
  • To verify the laws of equilibrium – the phrase ‘spring balance’ is not acceptable for ‘newton-metre’.
  • To measure the Focal length of a Concave Mirror or a Convex Lens.
    Note that when given the data for various values of u and v, you must calculate a value for f in each case, and only then find an average. (As opposed to averaging the u’s and the v’s and then just using the formula once to calculate f). Apparently the relevant phrase is “an average of an average is not an average”.

I have a document here which containts exam questions on every experiment which has ever appeared on a past paper from 2002 to 2010 (Higher Level and Ordinary Level) – this should be your bible for Section A over the coming weeks. Solutions are also included.

Now get back to work.

More to come.